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| 1 /* |
| 2 ** $Id: lgc.c,v 2.140 2013/03/16 21:10:18 roberto Exp $ |
| 3 ** Garbage Collector |
| 4 ** See Copyright Notice in lua.h |
| 5 */ |
| 6 |
| 7 #include <string.h> |
| 8 |
| 9 #define lgc_c |
| 10 #define LUA_CORE |
| 11 |
| 12 #include "lua.h" |
| 13 |
| 14 #include "ldebug.h" |
| 15 #include "ldo.h" |
| 16 #include "lfunc.h" |
| 17 #include "lgc.h" |
| 18 #include "lmem.h" |
| 19 #include "lobject.h" |
| 20 #include "lstate.h" |
| 21 #include "lstring.h" |
| 22 #include "ltable.h" |
| 23 #include "ltm.h" |
| 24 |
| 25 |
| 26 |
| 27 /* |
| 28 ** cost of sweeping one element (the size of a small object divided |
| 29 ** by some adjust for the sweep speed) |
| 30 */ |
| 31 #define GCSWEEPCOST ((sizeof(TString) + 4) / 4) |
| 32 |
| 33 /* maximum number of elements to sweep in each single step */ |
| 34 #define GCSWEEPMAX (cast_int((GCSTEPSIZE / GCSWEEPCOST) / 4)) |
| 35 |
| 36 /* maximum number of finalizers to call in each GC step */ |
| 37 #define GCFINALIZENUM 4 |
| 38 |
| 39 |
| 40 /* |
| 41 ** macro to adjust 'stepmul': 'stepmul' is actually used like |
| 42 ** 'stepmul / STEPMULADJ' (value chosen by tests) |
| 43 */ |
| 44 #define STEPMULADJ 200 |
| 45 |
| 46 |
| 47 /* |
| 48 ** macro to adjust 'pause': 'pause' is actually used like |
| 49 ** 'pause / PAUSEADJ' (value chosen by tests) |
| 50 */ |
| 51 #define PAUSEADJ 100 |
| 52 |
| 53 |
| 54 /* |
| 55 ** 'makewhite' erases all color bits plus the old bit and then |
| 56 ** sets only the current white bit |
| 57 */ |
| 58 #define maskcolors (~(bit2mask(BLACKBIT, OLDBIT) | WHITEBITS)) |
| 59 #define makewhite(g,x) \ |
| 60 (gch(x)->marked = cast_byte((gch(x)->marked & maskcolors) | luaC_white(g))) |
| 61 |
| 62 #define white2gray(x) resetbits(gch(x)->marked, WHITEBITS) |
| 63 #define black2gray(x) resetbit(gch(x)->marked, BLACKBIT) |
| 64 |
| 65 |
| 66 #define isfinalized(x) testbit(gch(x)->marked, FINALIZEDBIT) |
| 67 |
| 68 #define checkdeadkey(n) lua_assert(!ttisdeadkey(gkey(n)) || ttisnil(gval(n))) |
| 69 |
| 70 |
| 71 #define checkconsistency(obj) \ |
| 72 lua_longassert(!iscollectable(obj) || righttt(obj)) |
| 73 |
| 74 |
| 75 #define markvalue(g,o) { checkconsistency(o); \ |
| 76 if (valiswhite(o)) reallymarkobject(g,gcvalue(o)); } |
| 77 |
| 78 #define markobject(g,t) { if ((t) && iswhite(obj2gco(t))) \ |
| 79 reallymarkobject(g, obj2gco(t)); } |
| 80 |
| 81 static void reallymarkobject (global_State *g, GCObject *o); |
| 82 |
| 83 |
| 84 /* |
| 85 ** {====================================================== |
| 86 ** Generic functions |
| 87 ** ======================================================= |
| 88 */ |
| 89 |
| 90 |
| 91 /* |
| 92 ** one after last element in a hash array |
| 93 */ |
| 94 #define gnodelast(h) gnode(h, cast(size_t, sizenode(h))) |
| 95 |
| 96 |
| 97 /* |
| 98 ** link table 'h' into list pointed by 'p' |
| 99 */ |
| 100 #define linktable(h,p) ((h)->gclist = *(p), *(p) = obj2gco(h)) |
| 101 |
| 102 |
| 103 /* |
| 104 ** if key is not marked, mark its entry as dead (therefore removing it |
| 105 ** from the table) |
| 106 */ |
| 107 static void removeentry (Node *n) { |
| 108 lua_assert(ttisnil(gval(n))); |
| 109 if (valiswhite(gkey(n))) |
| 110 setdeadvalue(gkey(n)); /* unused and unmarked key; remove it */ |
| 111 } |
| 112 |
| 113 |
| 114 /* |
| 115 ** tells whether a key or value can be cleared from a weak |
| 116 ** table. Non-collectable objects are never removed from weak |
| 117 ** tables. Strings behave as `values', so are never removed too. for |
| 118 ** other objects: if really collected, cannot keep them; for objects |
| 119 ** being finalized, keep them in keys, but not in values |
| 120 */ |
| 121 static int iscleared (global_State *g, const TValue *o) { |
| 122 if (!iscollectable(o)) return 0; |
| 123 else if (ttisstring(o)) { |
| 124 markobject(g, rawtsvalue(o)); /* strings are `values', so are never weak */ |
| 125 return 0; |
| 126 } |
| 127 else return iswhite(gcvalue(o)); |
| 128 } |
| 129 |
| 130 |
| 131 /* |
| 132 ** barrier that moves collector forward, that is, mark the white object |
| 133 ** being pointed by a black object. |
| 134 */ |
| 135 void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v) { |
| 136 global_State *g = G(L); |
| 137 lua_assert(isblack(o) && iswhite(v) && !isdead(g, v) && !isdead(g, o)); |
| 138 lua_assert(g->gcstate != GCSpause); |
| 139 lua_assert(gch(o)->tt != LUA_TTABLE); |
| 140 if (keepinvariantout(g)) /* must keep invariant? */ |
| 141 reallymarkobject(g, v); /* restore invariant */ |
| 142 else { /* sweep phase */ |
| 143 lua_assert(issweepphase(g)); |
| 144 makewhite(g, o); /* mark main obj. as white to avoid other barriers */ |
| 145 } |
| 146 } |
| 147 |
| 148 |
| 149 /* |
| 150 ** barrier that moves collector backward, that is, mark the black object |
| 151 ** pointing to a white object as gray again. (Current implementation |
| 152 ** only works for tables; access to 'gclist' is not uniform across |
| 153 ** different types.) |
| 154 */ |
| 155 void luaC_barrierback_ (lua_State *L, GCObject *o) { |
| 156 global_State *g = G(L); |
| 157 lua_assert(isblack(o) && !isdead(g, o) && gch(o)->tt == LUA_TTABLE); |
| 158 black2gray(o); /* make object gray (again) */ |
| 159 gco2t(o)->gclist = g->grayagain; |
| 160 g->grayagain = o; |
| 161 } |
| 162 |
| 163 |
| 164 /* |
| 165 ** barrier for prototypes. When creating first closure (cache is |
| 166 ** NULL), use a forward barrier; this may be the only closure of the |
| 167 ** prototype (if it is a "regular" function, with a single instance) |
| 168 ** and the prototype may be big, so it is better to avoid traversing |
| 169 ** it again. Otherwise, use a backward barrier, to avoid marking all |
| 170 ** possible instances. |
| 171 */ |
| 172 LUAI_FUNC void luaC_barrierproto_ (lua_State *L, Proto *p, Closure *c) { |
| 173 global_State *g = G(L); |
| 174 lua_assert(isblack(obj2gco(p))); |
| 175 if (p->cache == NULL) { /* first time? */ |
| 176 luaC_objbarrier(L, p, c); |
| 177 } |
| 178 else { /* use a backward barrier */ |
| 179 black2gray(obj2gco(p)); /* make prototype gray (again) */ |
| 180 p->gclist = g->grayagain; |
| 181 g->grayagain = obj2gco(p); |
| 182 } |
| 183 } |
| 184 |
| 185 |
| 186 /* |
| 187 ** check color (and invariants) for an upvalue that was closed, |
| 188 ** i.e., moved into the 'allgc' list |
| 189 */ |
| 190 void luaC_checkupvalcolor (global_State *g, UpVal *uv) { |
| 191 GCObject *o = obj2gco(uv); |
| 192 lua_assert(!isblack(o)); /* open upvalues are never black */ |
| 193 if (isgray(o)) { |
| 194 if (keepinvariant(g)) { |
| 195 resetoldbit(o); /* see MOVE OLD rule */ |
| 196 gray2black(o); /* it is being visited now */ |
| 197 markvalue(g, uv->v); |
| 198 } |
| 199 else { |
| 200 lua_assert(issweepphase(g)); |
| 201 makewhite(g, o); |
| 202 } |
| 203 } |
| 204 } |
| 205 |
| 206 |
| 207 /* |
| 208 ** create a new collectable object (with given type and size) and link |
| 209 ** it to '*list'. 'offset' tells how many bytes to allocate before the |
| 210 ** object itself (used only by states). |
| 211 */ |
| 212 GCObject *luaC_newobj (lua_State *L, int tt, size_t sz, GCObject **list, |
| 213 int offset) { |
| 214 global_State *g = G(L); |
| 215 char *raw = cast(char *, luaM_newobject(L, novariant(tt), sz)); |
| 216 GCObject *o = obj2gco(raw + offset); |
| 217 if (list == NULL) |
| 218 list = &g->allgc; /* standard list for collectable objects */ |
| 219 gch(o)->marked = luaC_white(g); |
| 220 gch(o)->tt = tt; |
| 221 gch(o)->next = *list; |
| 222 *list = o; |
| 223 return o; |
| 224 } |
| 225 |
| 226 /* }====================================================== */ |
| 227 |
| 228 |
| 229 |
| 230 /* |
| 231 ** {====================================================== |
| 232 ** Mark functions |
| 233 ** ======================================================= |
| 234 */ |
| 235 |
| 236 |
| 237 /* |
| 238 ** mark an object. Userdata, strings, and closed upvalues are visited |
| 239 ** and turned black here. Other objects are marked gray and added |
| 240 ** to appropriate list to be visited (and turned black) later. (Open |
| 241 ** upvalues are already linked in 'headuv' list.) |
| 242 */ |
| 243 static void reallymarkobject (global_State *g, GCObject *o) { |
| 244 lu_mem size; |
| 245 white2gray(o); |
| 246 switch (gch(o)->tt) { |
| 247 case LUA_TSHRSTR: |
| 248 case LUA_TLNGSTR: { |
| 249 size = sizestring(gco2ts(o)); |
| 250 break; /* nothing else to mark; make it black */ |
| 251 } |
| 252 case LUA_TUSERDATA: { |
| 253 Table *mt = gco2u(o)->metatable; |
| 254 markobject(g, mt); |
| 255 markobject(g, gco2u(o)->env); |
| 256 size = sizeudata(gco2u(o)); |
| 257 break; |
| 258 } |
| 259 case LUA_TUPVAL: { |
| 260 UpVal *uv = gco2uv(o); |
| 261 markvalue(g, uv->v); |
| 262 if (uv->v != &uv->u.value) /* open? */ |
| 263 return; /* open upvalues remain gray */ |
| 264 size = sizeof(UpVal); |
| 265 break; |
| 266 } |
| 267 case LUA_TLCL: { |
| 268 gco2lcl(o)->gclist = g->gray; |
| 269 g->gray = o; |
| 270 return; |
| 271 } |
| 272 case LUA_TCCL: { |
| 273 gco2ccl(o)->gclist = g->gray; |
| 274 g->gray = o; |
| 275 return; |
| 276 } |
| 277 case LUA_TTABLE: { |
| 278 linktable(gco2t(o), &g->gray); |
| 279 return; |
| 280 } |
| 281 case LUA_TTHREAD: { |
| 282 gco2th(o)->gclist = g->gray; |
| 283 g->gray = o; |
| 284 return; |
| 285 } |
| 286 case LUA_TPROTO: { |
| 287 gco2p(o)->gclist = g->gray; |
| 288 g->gray = o; |
| 289 return; |
| 290 } |
| 291 default: lua_assert(0); return; |
| 292 } |
| 293 gray2black(o); |
| 294 g->GCmemtrav += size; |
| 295 } |
| 296 |
| 297 |
| 298 /* |
| 299 ** mark metamethods for basic types |
| 300 */ |
| 301 static void markmt (global_State *g) { |
| 302 int i; |
| 303 for (i=0; i < LUA_NUMTAGS; i++) |
| 304 markobject(g, g->mt[i]); |
| 305 } |
| 306 |
| 307 |
| 308 /* |
| 309 ** mark all objects in list of being-finalized |
| 310 */ |
| 311 static void markbeingfnz (global_State *g) { |
| 312 GCObject *o; |
| 313 for (o = g->tobefnz; o != NULL; o = gch(o)->next) { |
| 314 makewhite(g, o); |
| 315 reallymarkobject(g, o); |
| 316 } |
| 317 } |
| 318 |
| 319 |
| 320 /* |
| 321 ** mark all values stored in marked open upvalues. (See comment in |
| 322 ** 'lstate.h'.) |
| 323 */ |
| 324 static void remarkupvals (global_State *g) { |
| 325 UpVal *uv; |
| 326 for (uv = g->uvhead.u.l.next; uv != &g->uvhead; uv = uv->u.l.next) { |
| 327 if (isgray(obj2gco(uv))) |
| 328 markvalue(g, uv->v); |
| 329 } |
| 330 } |
| 331 |
| 332 |
| 333 /* |
| 334 ** mark root set and reset all gray lists, to start a new |
| 335 ** incremental (or full) collection |
| 336 */ |
| 337 static void restartcollection (global_State *g) { |
| 338 g->gray = g->grayagain = NULL; |
| 339 g->weak = g->allweak = g->ephemeron = NULL; |
| 340 markobject(g, g->mainthread); |
| 341 markvalue(g, &g->l_registry); |
| 342 markmt(g); |
| 343 markbeingfnz(g); /* mark any finalizing object left from previous cycle */ |
| 344 } |
| 345 |
| 346 /* }====================================================== */ |
| 347 |
| 348 |
| 349 /* |
| 350 ** {====================================================== |
| 351 ** Traverse functions |
| 352 ** ======================================================= |
| 353 */ |
| 354 |
| 355 static void traverseweakvalue (global_State *g, Table *h) { |
| 356 Node *n, *limit = gnodelast(h); |
| 357 /* if there is array part, assume it may have white values (do not |
| 358 traverse it just to check) */ |
| 359 int hasclears = (h->sizearray > 0); |
| 360 for (n = gnode(h, 0); n < limit; n++) { |
| 361 checkdeadkey(n); |
| 362 if (ttisnil(gval(n))) /* entry is empty? */ |
| 363 removeentry(n); /* remove it */ |
| 364 else { |
| 365 lua_assert(!ttisnil(gkey(n))); |
| 366 markvalue(g, gkey(n)); /* mark key */ |
| 367 if (!hasclears && iscleared(g, gval(n))) /* is there a white value? */ |
| 368 hasclears = 1; /* table will have to be cleared */ |
| 369 } |
| 370 } |
| 371 if (hasclears) |
| 372 linktable(h, &g->weak); /* has to be cleared later */ |
| 373 else /* no white values */ |
| 374 linktable(h, &g->grayagain); /* no need to clean */ |
| 375 } |
| 376 |
| 377 |
| 378 static int traverseephemeron (global_State *g, Table *h) { |
| 379 int marked = 0; /* true if an object is marked in this traversal */ |
| 380 int hasclears = 0; /* true if table has white keys */ |
| 381 int prop = 0; /* true if table has entry "white-key -> white-value" */ |
| 382 Node *n, *limit = gnodelast(h); |
| 383 int i; |
| 384 /* traverse array part (numeric keys are 'strong') */ |
| 385 for (i = 0; i < h->sizearray; i++) { |
| 386 if (valiswhite(&h->array[i])) { |
| 387 marked = 1; |
| 388 reallymarkobject(g, gcvalue(&h->array[i])); |
| 389 } |
| 390 } |
| 391 /* traverse hash part */ |
| 392 for (n = gnode(h, 0); n < limit; n++) { |
| 393 checkdeadkey(n); |
| 394 if (ttisnil(gval(n))) /* entry is empty? */ |
| 395 removeentry(n); /* remove it */ |
| 396 else if (iscleared(g, gkey(n))) { /* key is not marked (yet)? */ |
| 397 hasclears = 1; /* table must be cleared */ |
| 398 if (valiswhite(gval(n))) /* value not marked yet? */ |
| 399 prop = 1; /* must propagate again */ |
| 400 } |
| 401 else if (valiswhite(gval(n))) { /* value not marked yet? */ |
| 402 marked = 1; |
| 403 reallymarkobject(g, gcvalue(gval(n))); /* mark it now */ |
| 404 } |
| 405 } |
| 406 if (prop) |
| 407 linktable(h, &g->ephemeron); /* have to propagate again */ |
| 408 else if (hasclears) /* does table have white keys? */ |
| 409 linktable(h, &g->allweak); /* may have to clean white keys */ |
| 410 else /* no white keys */ |
| 411 linktable(h, &g->grayagain); /* no need to clean */ |
| 412 return marked; |
| 413 } |
| 414 |
| 415 |
| 416 static void traversestrongtable (global_State *g, Table *h) { |
| 417 Node *n, *limit = gnodelast(h); |
| 418 int i; |
| 419 for (i = 0; i < h->sizearray; i++) /* traverse array part */ |
| 420 markvalue(g, &h->array[i]); |
| 421 for (n = gnode(h, 0); n < limit; n++) { /* traverse hash part */ |
| 422 checkdeadkey(n); |
| 423 if (ttisnil(gval(n))) /* entry is empty? */ |
| 424 removeentry(n); /* remove it */ |
| 425 else { |
| 426 lua_assert(!ttisnil(gkey(n))); |
| 427 markvalue(g, gkey(n)); /* mark key */ |
| 428 markvalue(g, gval(n)); /* mark value */ |
| 429 } |
| 430 } |
| 431 } |
| 432 |
| 433 |
| 434 static lu_mem traversetable (global_State *g, Table *h) { |
| 435 const char *weakkey, *weakvalue; |
| 436 const TValue *mode = gfasttm(g, h->metatable, TM_MODE); |
| 437 markobject(g, h->metatable); |
| 438 if (mode && ttisstring(mode) && /* is there a weak mode? */ |
| 439 ((weakkey = strchr(svalue(mode), 'k')), |
| 440 (weakvalue = strchr(svalue(mode), 'v')), |
| 441 (weakkey || weakvalue))) { /* is really weak? */ |
| 442 black2gray(obj2gco(h)); /* keep table gray */ |
| 443 if (!weakkey) /* strong keys? */ |
| 444 traverseweakvalue(g, h); |
| 445 else if (!weakvalue) /* strong values? */ |
| 446 traverseephemeron(g, h); |
| 447 else /* all weak */ |
| 448 linktable(h, &g->allweak); /* nothing to traverse now */ |
| 449 } |
| 450 else /* not weak */ |
| 451 traversestrongtable(g, h); |
| 452 return sizeof(Table) + sizeof(TValue) * h->sizearray + |
| 453 sizeof(Node) * cast(size_t, sizenode(h)); |
| 454 } |
| 455 |
| 456 |
| 457 static int traverseproto (global_State *g, Proto *f) { |
| 458 int i; |
| 459 if (f->cache && iswhite(obj2gco(f->cache))) |
| 460 f->cache = NULL; /* allow cache to be collected */ |
| 461 markobject(g, f->source); |
| 462 for (i = 0; i < f->sizek; i++) /* mark literals */ |
| 463 markvalue(g, &f->k[i]); |
| 464 for (i = 0; i < f->sizeupvalues; i++) /* mark upvalue names */ |
| 465 markobject(g, f->upvalues[i].name); |
| 466 for (i = 0; i < f->sizep; i++) /* mark nested protos */ |
| 467 markobject(g, f->p[i]); |
| 468 for (i = 0; i < f->sizelocvars; i++) /* mark local-variable names */ |
| 469 markobject(g, f->locvars[i].varname); |
| 470 return sizeof(Proto) + sizeof(Instruction) * f->sizecode + |
| 471 sizeof(Proto *) * f->sizep + |
| 472 sizeof(TValue) * f->sizek + |
| 473 sizeof(int) * f->sizelineinfo + |
| 474 sizeof(LocVar) * f->sizelocvars + |
| 475 sizeof(Upvaldesc) * f->sizeupvalues; |
| 476 } |
| 477 |
| 478 |
| 479 static lu_mem traverseCclosure (global_State *g, CClosure *cl) { |
| 480 int i; |
| 481 for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */ |
| 482 markvalue(g, &cl->upvalue[i]); |
| 483 return sizeCclosure(cl->nupvalues); |
| 484 } |
| 485 |
| 486 static lu_mem traverseLclosure (global_State *g, LClosure *cl) { |
| 487 int i; |
| 488 markobject(g, cl->p); /* mark its prototype */ |
| 489 for (i = 0; i < cl->nupvalues; i++) /* mark its upvalues */ |
| 490 markobject(g, cl->upvals[i]); |
| 491 return sizeLclosure(cl->nupvalues); |
| 492 } |
| 493 |
| 494 |
| 495 static lu_mem traversestack (global_State *g, lua_State *th) { |
| 496 StkId o = th->stack; |
| 497 if (o == NULL) |
| 498 return 1; /* stack not completely built yet */ |
| 499 for (; o < th->top; o++) |
| 500 markvalue(g, o); |
| 501 if (g->gcstate == GCSatomic) { /* final traversal? */ |
| 502 StkId lim = th->stack + th->stacksize; /* real end of stack */ |
| 503 for (; o < lim; o++) /* clear not-marked stack slice */ |
| 504 setnilvalue(o); |
| 505 } |
| 506 return sizeof(lua_State) + sizeof(TValue) * th->stacksize; |
| 507 } |
| 508 |
| 509 |
| 510 /* |
| 511 ** traverse one gray object, turning it to black (except for threads, |
| 512 ** which are always gray). |
| 513 */ |
| 514 static void propagatemark (global_State *g) { |
| 515 lu_mem size; |
| 516 GCObject *o = g->gray; |
| 517 lua_assert(isgray(o)); |
| 518 gray2black(o); |
| 519 switch (gch(o)->tt) { |
| 520 case LUA_TTABLE: { |
| 521 Table *h = gco2t(o); |
| 522 g->gray = h->gclist; /* remove from 'gray' list */ |
| 523 size = traversetable(g, h); |
| 524 break; |
| 525 } |
| 526 case LUA_TLCL: { |
| 527 LClosure *cl = gco2lcl(o); |
| 528 g->gray = cl->gclist; /* remove from 'gray' list */ |
| 529 size = traverseLclosure(g, cl); |
| 530 break; |
| 531 } |
| 532 case LUA_TCCL: { |
| 533 CClosure *cl = gco2ccl(o); |
| 534 g->gray = cl->gclist; /* remove from 'gray' list */ |
| 535 size = traverseCclosure(g, cl); |
| 536 break; |
| 537 } |
| 538 case LUA_TTHREAD: { |
| 539 lua_State *th = gco2th(o); |
| 540 g->gray = th->gclist; /* remove from 'gray' list */ |
| 541 th->gclist = g->grayagain; |
| 542 g->grayagain = o; /* insert into 'grayagain' list */ |
| 543 black2gray(o); |
| 544 size = traversestack(g, th); |
| 545 break; |
| 546 } |
| 547 case LUA_TPROTO: { |
| 548 Proto *p = gco2p(o); |
| 549 g->gray = p->gclist; /* remove from 'gray' list */ |
| 550 size = traverseproto(g, p); |
| 551 break; |
| 552 } |
| 553 default: lua_assert(0); return; |
| 554 } |
| 555 g->GCmemtrav += size; |
| 556 } |
| 557 |
| 558 |
| 559 static void propagateall (global_State *g) { |
| 560 while (g->gray) propagatemark(g); |
| 561 } |
| 562 |
| 563 |
| 564 static void propagatelist (global_State *g, GCObject *l) { |
| 565 lua_assert(g->gray == NULL); /* no grays left */ |
| 566 g->gray = l; |
| 567 propagateall(g); /* traverse all elements from 'l' */ |
| 568 } |
| 569 |
| 570 /* |
| 571 ** retraverse all gray lists. Because tables may be reinserted in other |
| 572 ** lists when traversed, traverse the original lists to avoid traversing |
| 573 ** twice the same table (which is not wrong, but inefficient) |
| 574 */ |
| 575 static void retraversegrays (global_State *g) { |
| 576 GCObject *weak = g->weak; /* save original lists */ |
| 577 GCObject *grayagain = g->grayagain; |
| 578 GCObject *ephemeron = g->ephemeron; |
| 579 g->weak = g->grayagain = g->ephemeron = NULL; |
| 580 propagateall(g); /* traverse main gray list */ |
| 581 propagatelist(g, grayagain); |
| 582 propagatelist(g, weak); |
| 583 propagatelist(g, ephemeron); |
| 584 } |
| 585 |
| 586 |
| 587 static void convergeephemerons (global_State *g) { |
| 588 int changed; |
| 589 do { |
| 590 GCObject *w; |
| 591 GCObject *next = g->ephemeron; /* get ephemeron list */ |
| 592 g->ephemeron = NULL; /* tables will return to this list when traversed */ |
| 593 changed = 0; |
| 594 while ((w = next) != NULL) { |
| 595 next = gco2t(w)->gclist; |
| 596 if (traverseephemeron(g, gco2t(w))) { /* traverse marked some value? */ |
| 597 propagateall(g); /* propagate changes */ |
| 598 changed = 1; /* will have to revisit all ephemeron tables */ |
| 599 } |
| 600 } |
| 601 } while (changed); |
| 602 } |
| 603 |
| 604 /* }====================================================== */ |
| 605 |
| 606 |
| 607 /* |
| 608 ** {====================================================== |
| 609 ** Sweep Functions |
| 610 ** ======================================================= |
| 611 */ |
| 612 |
| 613 |
| 614 /* |
| 615 ** clear entries with unmarked keys from all weaktables in list 'l' up |
| 616 ** to element 'f' |
| 617 */ |
| 618 static void clearkeys (global_State *g, GCObject *l, GCObject *f) { |
| 619 for (; l != f; l = gco2t(l)->gclist) { |
| 620 Table *h = gco2t(l); |
| 621 Node *n, *limit = gnodelast(h); |
| 622 for (n = gnode(h, 0); n < limit; n++) { |
| 623 if (!ttisnil(gval(n)) && (iscleared(g, gkey(n)))) { |
| 624 setnilvalue(gval(n)); /* remove value ... */ |
| 625 removeentry(n); /* and remove entry from table */ |
| 626 } |
| 627 } |
| 628 } |
| 629 } |
| 630 |
| 631 |
| 632 /* |
| 633 ** clear entries with unmarked values from all weaktables in list 'l' up |
| 634 ** to element 'f' |
| 635 */ |
| 636 static void clearvalues (global_State *g, GCObject *l, GCObject *f) { |
| 637 for (; l != f; l = gco2t(l)->gclist) { |
| 638 Table *h = gco2t(l); |
| 639 Node *n, *limit = gnodelast(h); |
| 640 int i; |
| 641 for (i = 0; i < h->sizearray; i++) { |
| 642 TValue *o = &h->array[i]; |
| 643 if (iscleared(g, o)) /* value was collected? */ |
| 644 setnilvalue(o); /* remove value */ |
| 645 } |
| 646 for (n = gnode(h, 0); n < limit; n++) { |
| 647 if (!ttisnil(gval(n)) && iscleared(g, gval(n))) { |
| 648 setnilvalue(gval(n)); /* remove value ... */ |
| 649 removeentry(n); /* and remove entry from table */ |
| 650 } |
| 651 } |
| 652 } |
| 653 } |
| 654 |
| 655 |
| 656 static void freeobj (lua_State *L, GCObject *o) { |
| 657 switch (gch(o)->tt) { |
| 658 case LUA_TPROTO: luaF_freeproto(L, gco2p(o)); break; |
| 659 case LUA_TLCL: { |
| 660 luaM_freemem(L, o, sizeLclosure(gco2lcl(o)->nupvalues)); |
| 661 break; |
| 662 } |
| 663 case LUA_TCCL: { |
| 664 luaM_freemem(L, o, sizeCclosure(gco2ccl(o)->nupvalues)); |
| 665 break; |
| 666 } |
| 667 case LUA_TUPVAL: luaF_freeupval(L, gco2uv(o)); break; |
| 668 case LUA_TTABLE: luaH_free(L, gco2t(o)); break; |
| 669 case LUA_TTHREAD: luaE_freethread(L, gco2th(o)); break; |
| 670 case LUA_TUSERDATA: luaM_freemem(L, o, sizeudata(gco2u(o))); break; |
| 671 case LUA_TSHRSTR: |
| 672 G(L)->strt.nuse--; |
| 673 /* go through */ |
| 674 case LUA_TLNGSTR: { |
| 675 luaM_freemem(L, o, sizestring(gco2ts(o))); |
| 676 break; |
| 677 } |
| 678 default: lua_assert(0); |
| 679 } |
| 680 } |
| 681 |
| 682 |
| 683 #define sweepwholelist(L,p) sweeplist(L,p,MAX_LUMEM) |
| 684 static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count); |
| 685 |
| 686 |
| 687 /* |
| 688 ** sweep the (open) upvalues of a thread and resize its stack and |
| 689 ** list of call-info structures. |
| 690 */ |
| 691 static void sweepthread (lua_State *L, lua_State *L1) { |
| 692 if (L1->stack == NULL) return; /* stack not completely built yet */ |
| 693 sweepwholelist(L, &L1->openupval); /* sweep open upvalues */ |
| 694 luaE_freeCI(L1); /* free extra CallInfo slots */ |
| 695 /* should not change the stack during an emergency gc cycle */ |
| 696 if (G(L)->gckind != KGC_EMERGENCY) |
| 697 luaD_shrinkstack(L1); |
| 698 } |
| 699 |
| 700 |
| 701 /* |
| 702 ** sweep at most 'count' elements from a list of GCObjects erasing dead |
| 703 ** objects, where a dead (not alive) object is one marked with the "old" |
| 704 ** (non current) white and not fixed. |
| 705 ** In non-generational mode, change all non-dead objects back to white, |
| 706 ** preparing for next collection cycle. |
| 707 ** In generational mode, keep black objects black, and also mark them as |
| 708 ** old; stop when hitting an old object, as all objects after that |
| 709 ** one will be old too. |
| 710 ** When object is a thread, sweep its list of open upvalues too. |
| 711 */ |
| 712 static GCObject **sweeplist (lua_State *L, GCObject **p, lu_mem count) { |
| 713 global_State *g = G(L); |
| 714 int ow = otherwhite(g); |
| 715 int toclear, toset; /* bits to clear and to set in all live objects */ |
| 716 int tostop; /* stop sweep when this is true */ |
| 717 if (isgenerational(g)) { /* generational mode? */ |
| 718 toclear = ~0; /* clear nothing */ |
| 719 toset = bitmask(OLDBIT); /* set the old bit of all surviving objects */ |
| 720 tostop = bitmask(OLDBIT); /* do not sweep old generation */ |
| 721 } |
| 722 else { /* normal mode */ |
| 723 toclear = maskcolors; /* clear all color bits + old bit */ |
| 724 toset = luaC_white(g); /* make object white */ |
| 725 tostop = 0; /* do not stop */ |
| 726 } |
| 727 while (*p != NULL && count-- > 0) { |
| 728 GCObject *curr = *p; |
| 729 int marked = gch(curr)->marked; |
| 730 if (isdeadm(ow, marked)) { /* is 'curr' dead? */ |
| 731 *p = gch(curr)->next; /* remove 'curr' from list */ |
| 732 freeobj(L, curr); /* erase 'curr' */ |
| 733 } |
| 734 else { |
| 735 if (testbits(marked, tostop)) |
| 736 return NULL; /* stop sweeping this list */ |
| 737 if (gch(curr)->tt == LUA_TTHREAD) |
| 738 sweepthread(L, gco2th(curr)); /* sweep thread's upvalues */ |
| 739 /* update marks */ |
| 740 gch(curr)->marked = cast_byte((marked & toclear) | toset); |
| 741 p = &gch(curr)->next; /* go to next element */ |
| 742 } |
| 743 } |
| 744 return (*p == NULL) ? NULL : p; |
| 745 } |
| 746 |
| 747 |
| 748 /* |
| 749 ** sweep a list until a live object (or end of list) |
| 750 */ |
| 751 static GCObject **sweeptolive (lua_State *L, GCObject **p, int *n) { |
| 752 GCObject ** old = p; |
| 753 int i = 0; |
| 754 do { |
| 755 i++; |
| 756 p = sweeplist(L, p, 1); |
| 757 } while (p == old); |
| 758 if (n) *n += i; |
| 759 return p; |
| 760 } |
| 761 |
| 762 /* }====================================================== */ |
| 763 |
| 764 |
| 765 /* |
| 766 ** {====================================================== |
| 767 ** Finalization |
| 768 ** ======================================================= |
| 769 */ |
| 770 |
| 771 static void checkSizes (lua_State *L) { |
| 772 global_State *g = G(L); |
| 773 if (g->gckind != KGC_EMERGENCY) { /* do not change sizes in emergency */ |
| 774 int hs = g->strt.size / 2; /* half the size of the string table */ |
| 775 if (g->strt.nuse < cast(lu_int32, hs)) /* using less than that half? */ |
| 776 luaS_resize(L, hs); /* halve its size */ |
| 777 luaZ_freebuffer(L, &g->buff); /* free concatenation buffer */ |
| 778 } |
| 779 } |
| 780 |
| 781 |
| 782 static GCObject *udata2finalize (global_State *g) { |
| 783 GCObject *o = g->tobefnz; /* get first element */ |
| 784 lua_assert(isfinalized(o)); |
| 785 g->tobefnz = gch(o)->next; /* remove it from 'tobefnz' list */ |
| 786 gch(o)->next = g->allgc; /* return it to 'allgc' list */ |
| 787 g->allgc = o; |
| 788 resetbit(gch(o)->marked, SEPARATED); /* mark that it is not in 'tobefnz' */ |
| 789 lua_assert(!isold(o)); /* see MOVE OLD rule */ |
| 790 if (!keepinvariantout(g)) /* not keeping invariant? */ |
| 791 makewhite(g, o); /* "sweep" object */ |
| 792 return o; |
| 793 } |
| 794 |
| 795 |
| 796 static void dothecall (lua_State *L, void *ud) { |
| 797 UNUSED(ud); |
| 798 luaD_call(L, L->top - 2, 0, 0); |
| 799 } |
| 800 |
| 801 |
| 802 static void GCTM (lua_State *L, int propagateerrors) { |
| 803 global_State *g = G(L); |
| 804 const TValue *tm; |
| 805 TValue v; |
| 806 setgcovalue(L, &v, udata2finalize(g)); |
| 807 tm = luaT_gettmbyobj(L, &v, TM_GC); |
| 808 if (tm != NULL && ttisfunction(tm)) { /* is there a finalizer? */ |
| 809 int status; |
| 810 lu_byte oldah = L->allowhook; |
| 811 int running = g->gcrunning; |
| 812 L->allowhook = 0; /* stop debug hooks during GC metamethod */ |
| 813 g->gcrunning = 0; /* avoid GC steps */ |
| 814 setobj2s(L, L->top, tm); /* push finalizer... */ |
| 815 setobj2s(L, L->top + 1, &v); /* ... and its argument */ |
| 816 L->top += 2; /* and (next line) call the finalizer */ |
| 817 status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0); |
| 818 L->allowhook = oldah; /* restore hooks */ |
| 819 g->gcrunning = running; /* restore state */ |
| 820 if (status != LUA_OK && propagateerrors) { /* error while running __gc? */ |
| 821 if (status == LUA_ERRRUN) { /* is there an error object? */ |
| 822 const char *msg = (ttisstring(L->top - 1)) |
| 823 ? svalue(L->top - 1) |
| 824 : "no message"; |
| 825 luaO_pushfstring(L, "error in __gc metamethod (%s)", msg); |
| 826 status = LUA_ERRGCMM; /* error in __gc metamethod */ |
| 827 } |
| 828 luaD_throw(L, status); /* re-throw error */ |
| 829 } |
| 830 } |
| 831 } |
| 832 |
| 833 |
| 834 /* |
| 835 ** move all unreachable objects (or 'all' objects) that need |
| 836 ** finalization from list 'finobj' to list 'tobefnz' (to be finalized) |
| 837 */ |
| 838 static void separatetobefnz (lua_State *L, int all) { |
| 839 global_State *g = G(L); |
| 840 GCObject **p = &g->finobj; |
| 841 GCObject *curr; |
| 842 GCObject **lastnext = &g->tobefnz; |
| 843 /* find last 'next' field in 'tobefnz' list (to add elements in its end) */ |
| 844 while (*lastnext != NULL) |
| 845 lastnext = &gch(*lastnext)->next; |
| 846 while ((curr = *p) != NULL) { /* traverse all finalizable objects */ |
| 847 lua_assert(!isfinalized(curr)); |
| 848 lua_assert(testbit(gch(curr)->marked, SEPARATED)); |
| 849 if (!(iswhite(curr) || all)) /* not being collected? */ |
| 850 p = &gch(curr)->next; /* don't bother with it */ |
| 851 else { |
| 852 l_setbit(gch(curr)->marked, FINALIZEDBIT); /* won't be finalized again */ |
| 853 *p = gch(curr)->next; /* remove 'curr' from 'finobj' list */ |
| 854 gch(curr)->next = *lastnext; /* link at the end of 'tobefnz' list */ |
| 855 *lastnext = curr; |
| 856 lastnext = &gch(curr)->next; |
| 857 } |
| 858 } |
| 859 } |
| 860 |
| 861 |
| 862 /* |
| 863 ** if object 'o' has a finalizer, remove it from 'allgc' list (must |
| 864 ** search the list to find it) and link it in 'finobj' list. |
| 865 */ |
| 866 void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) { |
| 867 global_State *g = G(L); |
| 868 if (testbit(gch(o)->marked, SEPARATED) || /* obj. is already separated... */ |
| 869 isfinalized(o) || /* ... or is finalized... */ |
| 870 gfasttm(g, mt, TM_GC) == NULL) /* or has no finalizer? */ |
| 871 return; /* nothing to be done */ |
| 872 else { /* move 'o' to 'finobj' list */ |
| 873 GCObject **p; |
| 874 GCheader *ho = gch(o); |
| 875 if (g->sweepgc == &ho->next) { /* avoid removing current sweep object */ |
| 876 lua_assert(issweepphase(g)); |
| 877 g->sweepgc = sweeptolive(L, g->sweepgc, NULL); |
| 878 } |
| 879 /* search for pointer pointing to 'o' */ |
| 880 for (p = &g->allgc; *p != o; p = &gch(*p)->next) { /* empty */ } |
| 881 *p = ho->next; /* remove 'o' from root list */ |
| 882 ho->next = g->finobj; /* link it in list 'finobj' */ |
| 883 g->finobj = o; |
| 884 l_setbit(ho->marked, SEPARATED); /* mark it as such */ |
| 885 if (!keepinvariantout(g)) /* not keeping invariant? */ |
| 886 makewhite(g, o); /* "sweep" object */ |
| 887 else |
| 888 resetoldbit(o); /* see MOVE OLD rule */ |
| 889 } |
| 890 } |
| 891 |
| 892 /* }====================================================== */ |
| 893 |
| 894 |
| 895 /* |
| 896 ** {====================================================== |
| 897 ** GC control |
| 898 ** ======================================================= |
| 899 */ |
| 900 |
| 901 |
| 902 /* |
| 903 ** set a reasonable "time" to wait before starting a new GC cycle; |
| 904 ** cycle will start when memory use hits threshold |
| 905 */ |
| 906 static void setpause (global_State *g, l_mem estimate) { |
| 907 l_mem debt, threshold; |
| 908 estimate = estimate / PAUSEADJ; /* adjust 'estimate' */ |
| 909 threshold = (g->gcpause < MAX_LMEM / estimate) /* overflow? */ |
| 910 ? estimate * g->gcpause /* no overflow */ |
| 911 : MAX_LMEM; /* overflow; truncate to maximum */ |
| 912 debt = -cast(l_mem, threshold - gettotalbytes(g)); |
| 913 luaE_setdebt(g, debt); |
| 914 } |
| 915 |
| 916 |
| 917 #define sweepphases \ |
| 918 (bitmask(GCSsweepstring) | bitmask(GCSsweepudata) | bitmask(GCSsweep)) |
| 919 |
| 920 |
| 921 /* |
| 922 ** enter first sweep phase (strings) and prepare pointers for other |
| 923 ** sweep phases. The calls to 'sweeptolive' make pointers point to an |
| 924 ** object inside the list (instead of to the header), so that the real |
| 925 ** sweep do not need to skip objects created between "now" and the start |
| 926 ** of the real sweep. |
| 927 ** Returns how many objects it swept. |
| 928 */ |
| 929 static int entersweep (lua_State *L) { |
| 930 global_State *g = G(L); |
| 931 int n = 0; |
| 932 g->gcstate = GCSsweepstring; |
| 933 lua_assert(g->sweepgc == NULL && g->sweepfin == NULL); |
| 934 /* prepare to sweep strings, finalizable objects, and regular objects */ |
| 935 g->sweepstrgc = 0; |
| 936 g->sweepfin = sweeptolive(L, &g->finobj, &n); |
| 937 g->sweepgc = sweeptolive(L, &g->allgc, &n); |
| 938 return n; |
| 939 } |
| 940 |
| 941 |
| 942 /* |
| 943 ** change GC mode |
| 944 */ |
| 945 void luaC_changemode (lua_State *L, int mode) { |
| 946 global_State *g = G(L); |
| 947 if (mode == g->gckind) return; /* nothing to change */ |
| 948 if (mode == KGC_GEN) { /* change to generational mode */ |
| 949 /* make sure gray lists are consistent */ |
| 950 luaC_runtilstate(L, bitmask(GCSpropagate)); |
| 951 g->GCestimate = gettotalbytes(g); |
| 952 g->gckind = KGC_GEN; |
| 953 } |
| 954 else { /* change to incremental mode */ |
| 955 /* sweep all objects to turn them back to white |
| 956 (as white has not changed, nothing extra will be collected) */ |
| 957 g->gckind = KGC_NORMAL; |
| 958 entersweep(L); |
| 959 luaC_runtilstate(L, ~sweepphases); |
| 960 } |
| 961 } |
| 962 |
| 963 |
| 964 /* |
| 965 ** call all pending finalizers |
| 966 */ |
| 967 static void callallpendingfinalizers (lua_State *L, int propagateerrors) { |
| 968 global_State *g = G(L); |
| 969 while (g->tobefnz) { |
| 970 resetoldbit(g->tobefnz); |
| 971 GCTM(L, propagateerrors); |
| 972 } |
| 973 } |
| 974 |
| 975 |
| 976 void luaC_freeallobjects (lua_State *L) { |
| 977 global_State *g = G(L); |
| 978 int i; |
| 979 separatetobefnz(L, 1); /* separate all objects with finalizers */ |
| 980 lua_assert(g->finobj == NULL); |
| 981 callallpendingfinalizers(L, 0); |
| 982 g->currentwhite = WHITEBITS; /* this "white" makes all objects look dead */ |
| 983 g->gckind = KGC_NORMAL; |
| 984 sweepwholelist(L, &g->finobj); /* finalizers can create objs. in 'finobj' */ |
| 985 sweepwholelist(L, &g->allgc); |
| 986 for (i = 0; i < g->strt.size; i++) /* free all string lists */ |
| 987 sweepwholelist(L, &g->strt.hash[i]); |
| 988 lua_assert(g->strt.nuse == 0); |
| 989 } |
| 990 |
| 991 |
| 992 static l_mem atomic (lua_State *L) { |
| 993 global_State *g = G(L); |
| 994 l_mem work = -cast(l_mem, g->GCmemtrav); /* start counting work */ |
| 995 GCObject *origweak, *origall; |
| 996 lua_assert(!iswhite(obj2gco(g->mainthread))); |
| 997 markobject(g, L); /* mark running thread */ |
| 998 /* registry and global metatables may be changed by API */ |
| 999 markvalue(g, &g->l_registry); |
| 1000 markmt(g); /* mark basic metatables */ |
| 1001 /* remark occasional upvalues of (maybe) dead threads */ |
| 1002 remarkupvals(g); |
| 1003 propagateall(g); /* propagate changes */ |
| 1004 work += g->GCmemtrav; /* stop counting (do not (re)count grays) */ |
| 1005 /* traverse objects caught by write barrier and by 'remarkupvals' */ |
| 1006 retraversegrays(g); |
| 1007 work -= g->GCmemtrav; /* restart counting */ |
| 1008 convergeephemerons(g); |
| 1009 /* at this point, all strongly accessible objects are marked. */ |
| 1010 /* clear values from weak tables, before checking finalizers */ |
| 1011 clearvalues(g, g->weak, NULL); |
| 1012 clearvalues(g, g->allweak, NULL); |
| 1013 origweak = g->weak; origall = g->allweak; |
| 1014 work += g->GCmemtrav; /* stop counting (objects being finalized) */ |
| 1015 separatetobefnz(L, 0); /* separate objects to be finalized */ |
| 1016 markbeingfnz(g); /* mark objects that will be finalized */ |
| 1017 propagateall(g); /* remark, to propagate `preserveness' */ |
| 1018 work -= g->GCmemtrav; /* restart counting */ |
| 1019 convergeephemerons(g); |
| 1020 /* at this point, all resurrected objects are marked. */ |
| 1021 /* remove dead objects from weak tables */ |
| 1022 clearkeys(g, g->ephemeron, NULL); /* clear keys from all ephemeron tables */ |
| 1023 clearkeys(g, g->allweak, NULL); /* clear keys from all allweak tables */ |
| 1024 /* clear values from resurrected weak tables */ |
| 1025 clearvalues(g, g->weak, origweak); |
| 1026 clearvalues(g, g->allweak, origall); |
| 1027 g->currentwhite = cast_byte(otherwhite(g)); /* flip current white */ |
| 1028 work += g->GCmemtrav; /* complete counting */ |
| 1029 return work; /* estimate of memory marked by 'atomic' */ |
| 1030 } |
| 1031 |
| 1032 |
| 1033 static lu_mem singlestep (lua_State *L) { |
| 1034 global_State *g = G(L); |
| 1035 switch (g->gcstate) { |
| 1036 case GCSpause: { |
| 1037 /* start to count memory traversed */ |
| 1038 g->GCmemtrav = g->strt.size * sizeof(GCObject*); |
| 1039 lua_assert(!isgenerational(g)); |
| 1040 restartcollection(g); |
| 1041 g->gcstate = GCSpropagate; |
| 1042 return g->GCmemtrav; |
| 1043 } |
| 1044 case GCSpropagate: { |
| 1045 if (g->gray) { |
| 1046 lu_mem oldtrav = g->GCmemtrav; |
| 1047 propagatemark(g); |
| 1048 return g->GCmemtrav - oldtrav; /* memory traversed in this step */ |
| 1049 } |
| 1050 else { /* no more `gray' objects */ |
| 1051 lu_mem work; |
| 1052 int sw; |
| 1053 g->gcstate = GCSatomic; /* finish mark phase */ |
| 1054 g->GCestimate = g->GCmemtrav; /* save what was counted */; |
| 1055 work = atomic(L); /* add what was traversed by 'atomic' */ |
| 1056 g->GCestimate += work; /* estimate of total memory traversed */ |
| 1057 sw = entersweep(L); |
| 1058 return work + sw * GCSWEEPCOST; |
| 1059 } |
| 1060 } |
| 1061 case GCSsweepstring: { |
| 1062 int i; |
| 1063 for (i = 0; i < GCSWEEPMAX && g->sweepstrgc + i < g->strt.size; i++) |
| 1064 sweepwholelist(L, &g->strt.hash[g->sweepstrgc + i]); |
| 1065 g->sweepstrgc += i; |
| 1066 if (g->sweepstrgc >= g->strt.size) /* no more strings to sweep? */ |
| 1067 g->gcstate = GCSsweepudata; |
| 1068 return i * GCSWEEPCOST; |
| 1069 } |
| 1070 case GCSsweepudata: { |
| 1071 if (g->sweepfin) { |
| 1072 g->sweepfin = sweeplist(L, g->sweepfin, GCSWEEPMAX); |
| 1073 return GCSWEEPMAX*GCSWEEPCOST; |
| 1074 } |
| 1075 else { |
| 1076 g->gcstate = GCSsweep; |
| 1077 return 0; |
| 1078 } |
| 1079 } |
| 1080 case GCSsweep: { |
| 1081 if (g->sweepgc) { |
| 1082 g->sweepgc = sweeplist(L, g->sweepgc, GCSWEEPMAX); |
| 1083 return GCSWEEPMAX*GCSWEEPCOST; |
| 1084 } |
| 1085 else { |
| 1086 /* sweep main thread */ |
| 1087 GCObject *mt = obj2gco(g->mainthread); |
| 1088 sweeplist(L, &mt, 1); |
| 1089 checkSizes(L); |
| 1090 g->gcstate = GCSpause; /* finish collection */ |
| 1091 return GCSWEEPCOST; |
| 1092 } |
| 1093 } |
| 1094 default: lua_assert(0); return 0; |
| 1095 } |
| 1096 } |
| 1097 |
| 1098 |
| 1099 /* |
| 1100 ** advances the garbage collector until it reaches a state allowed |
| 1101 ** by 'statemask' |
| 1102 */ |
| 1103 void luaC_runtilstate (lua_State *L, int statesmask) { |
| 1104 global_State *g = G(L); |
| 1105 while (!testbit(statesmask, g->gcstate)) |
| 1106 singlestep(L); |
| 1107 } |
| 1108 |
| 1109 |
| 1110 static void generationalcollection (lua_State *L) { |
| 1111 global_State *g = G(L); |
| 1112 lua_assert(g->gcstate == GCSpropagate); |
| 1113 if (g->GCestimate == 0) { /* signal for another major collection? */ |
| 1114 luaC_fullgc(L, 0); /* perform a full regular collection */ |
| 1115 g->GCestimate = gettotalbytes(g); /* update control */ |
| 1116 } |
| 1117 else { |
| 1118 lu_mem estimate = g->GCestimate; |
| 1119 luaC_runtilstate(L, bitmask(GCSpause)); /* run complete (minor) cycle */ |
| 1120 g->gcstate = GCSpropagate; /* skip restart */ |
| 1121 if (gettotalbytes(g) > (estimate / 100) * g->gcmajorinc) |
| 1122 g->GCestimate = 0; /* signal for a major collection */ |
| 1123 else |
| 1124 g->GCestimate = estimate; /* keep estimate from last major coll. */ |
| 1125 |
| 1126 } |
| 1127 setpause(g, gettotalbytes(g)); |
| 1128 lua_assert(g->gcstate == GCSpropagate); |
| 1129 } |
| 1130 |
| 1131 |
| 1132 static void incstep (lua_State *L) { |
| 1133 global_State *g = G(L); |
| 1134 l_mem debt = g->GCdebt; |
| 1135 int stepmul = g->gcstepmul; |
| 1136 if (stepmul < 40) stepmul = 40; /* avoid ridiculous low values (and 0) */ |
| 1137 /* convert debt from Kb to 'work units' (avoid zero debt and overflows) */ |
| 1138 debt = (debt / STEPMULADJ) + 1; |
| 1139 debt = (debt < MAX_LMEM / stepmul) ? debt * stepmul : MAX_LMEM; |
| 1140 do { /* always perform at least one single step */ |
| 1141 lu_mem work = singlestep(L); /* do some work */ |
| 1142 debt -= work; |
| 1143 } while (debt > -GCSTEPSIZE && g->gcstate != GCSpause); |
| 1144 if (g->gcstate == GCSpause) |
| 1145 setpause(g, g->GCestimate); /* pause until next cycle */ |
| 1146 else { |
| 1147 debt = (debt / stepmul) * STEPMULADJ; /* convert 'work units' to Kb */ |
| 1148 luaE_setdebt(g, debt); |
| 1149 } |
| 1150 } |
| 1151 |
| 1152 |
| 1153 /* |
| 1154 ** performs a basic GC step |
| 1155 */ |
| 1156 void luaC_forcestep (lua_State *L) { |
| 1157 global_State *g = G(L); |
| 1158 int i; |
| 1159 if (isgenerational(g)) generationalcollection(L); |
| 1160 else incstep(L); |
| 1161 /* run a few finalizers (or all of them at the end of a collect cycle) */ |
| 1162 for (i = 0; g->tobefnz && (i < GCFINALIZENUM || g->gcstate == GCSpause); i++) |
| 1163 GCTM(L, 1); /* call one finalizer */ |
| 1164 } |
| 1165 |
| 1166 |
| 1167 /* |
| 1168 ** performs a basic GC step only if collector is running |
| 1169 */ |
| 1170 void luaC_step (lua_State *L) { |
| 1171 global_State *g = G(L); |
| 1172 if (g->gcrunning) luaC_forcestep(L); |
| 1173 else luaE_setdebt(g, -GCSTEPSIZE); /* avoid being called too often */ |
| 1174 } |
| 1175 |
| 1176 |
| 1177 |
| 1178 /* |
| 1179 ** performs a full GC cycle; if "isemergency", does not call |
| 1180 ** finalizers (which could change stack positions) |
| 1181 */ |
| 1182 void luaC_fullgc (lua_State *L, int isemergency) { |
| 1183 global_State *g = G(L); |
| 1184 int origkind = g->gckind; |
| 1185 lua_assert(origkind != KGC_EMERGENCY); |
| 1186 if (isemergency) /* do not run finalizers during emergency GC */ |
| 1187 g->gckind = KGC_EMERGENCY; |
| 1188 else { |
| 1189 g->gckind = KGC_NORMAL; |
| 1190 callallpendingfinalizers(L, 1); |
| 1191 } |
| 1192 if (keepinvariant(g)) { /* may there be some black objects? */ |
| 1193 /* must sweep all objects to turn them back to white |
| 1194 (as white has not changed, nothing will be collected) */ |
| 1195 entersweep(L); |
| 1196 } |
| 1197 /* finish any pending sweep phase to start a new cycle */ |
| 1198 luaC_runtilstate(L, bitmask(GCSpause)); |
| 1199 luaC_runtilstate(L, ~bitmask(GCSpause)); /* start new collection */ |
| 1200 luaC_runtilstate(L, bitmask(GCSpause)); /* run entire collection */ |
| 1201 if (origkind == KGC_GEN) { /* generational mode? */ |
| 1202 /* generational mode must be kept in propagate phase */ |
| 1203 luaC_runtilstate(L, bitmask(GCSpropagate)); |
| 1204 } |
| 1205 g->gckind = origkind; |
| 1206 setpause(g, gettotalbytes(g)); |
| 1207 if (!isemergency) /* do not run finalizers during emergency GC */ |
| 1208 callallpendingfinalizers(L, 1); |
| 1209 } |
| 1210 |
| 1211 /* }====================================================== */ |
| 1212 |
| 1213 |
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